Hydraulically operated enginepropeller control



Oct. 7,1952 V D. A. RICHARDSON 2,612,958

HYDRAULICALLY OPERATED ENGINE-PROPELLER CONTROL Filed Aug. 30, 1945 8 Sheets-Sheet l Z if OC- 7, 1952 D. A. RICHARDSON 2,512,953

HYDRAULICALLY OPERATED ENGINE-PROPELLER CONTROL Oct. 7, 1952 D. A. RICHARDSON 2,612,958

HYDRAULICALLY OPERATED ENGINE-PROP'ELLER CONTROL Filed Aug. so, 1945 a s heetsvsheet 4 ATTORNEY Oct. 7, 1952 D. A, RlcHARDsoN 2,612,958

HYDRAULICALLY OPERATED ENGINE-PROPELLER CONTROL Filed Aug. zo, 1945 8 sheets-sheet 5 WKN Oct. 7, 1952 D. A. RlcHARDsoN 2,612,958

` HYDRAULICALLY OPERATED ENGINE-PROPELLER CONTROL Filed Aug. 3o, 1945 e sheets-sheet `e INVENTOR l oct. 7, 1952 D. A. RICHARDSON HYDRAULICALLY OPERATED ENGINE-PROPELLER CONTROL 8 Sheets-Sheet 7 Filed Aug. .30, 1945 FEE gaf WL ya@ @Q43 HYDRAULICALLY OPERATEID ENGINE-PROPELLER CONTROL 8 Sheets-Sheet 8 D. A. RICHARDSON l En we uwer or for ae Filed Aug. 30, 1945 Oct. 7, 1952 NNN f/, Y INVENTOR 42 ATToRNEY// Patented ct. 7, 19h52 `HalimiULICA,LLv OPERATED ENGINE- PROPELLER ooNIRoL `David A. "Richardson, Dayton, Ohio, assigner to General Motors ,Corporation, DetroitpMioh-.ra

corporation offDelaware Application August 30, 1945, Serial No. 613,563 i115 :C lams. (Cl. 1Z0-160.213)

j'IFhis invention relates to a 4system loi' `control for prime-mover-propeller power plants-particsularly-forusein airplanes.

An object of -the invent-ion is to provide as ysltem of control having speed responsive 'means for governing the speed of the prime-mover "th-rough automatic control of bla-d e anglein order to maintain a manually selected nspeed -wh--le providing also for control of 'bladeangle independently 4of -the speed responsive means Vunder certain conditions', namely; 4(l) under idling condition, when the-'speed responsive means may lnot have control of blade angle, positively to obtain a iminimum blade angle required V13o-,main- -tanoperation Vof the prime-mover; (2') onder engine startingconditiona positively to obtain a blade angle requiring the least torque output to the propeller -in order Ato 'facilitate starting and providing for lmaintenance `of operation o f the `prime-mover when :it becomes self-operative; C39 under conditions of low blade angle -as may 'be `required for vbraking in flight or 4during "landving with maximum prime-mover speed (limited for .example `by an automatic -sfuel control) Ito provide for manual selection of a bla-de angle suitable for braking; (4) when taxying to provide manual control for Iforward :motion of the lairplane, `ferrer/verse .or .braking and for stopping; 165i under condition fof `failure of the speed `reaponsive governorproperly to limit fbladeangles `in `the higher range, manually to set the limits `,of high blade angles;` undercondition of :failure of .the governor toobtain the 'high blade .angle required vfor ffeathering, manually tooondiztioriwthe. system lto effect teathering independent- :lvofthegovernor. Y

in connection with .the accomplishment of the foregoingobieots, it is a further object to pro- `:vide for `minimis ing the effect upon the speed responsive ,governor of the operation of hy.- ,drooloehll? operated blade-:angle-setting torque Wboh `the governor controls. To this end. @een erltilwentionprovides an hydraulic sys.- tem ortho governor .independent .of .thehadraur Alie. erstem .for tbe torque units, The latter system .-f, ,ludos `a Adistr ibutirle valve for `oon- -trollne tbe torque units .for pitch L' easing or decreasing `tunedons. Trie ,distribulm val-ve is under control by :a .differential meobonismrrespondirlg .to two movements, one movement-being eieot've to demand e blade anale change and other movement :responding .to blade anale etrange 'to .restore the distributing :valve to eouiln trium status when the demand ,has been satisned- (Tbe demanding movement .is under o, o1 by the governor and by independerltfmeans which `positively enforces lor limits a :demand under foonditions mentioned in the preceding paragraph. More specifically `the demanding movement is that of Aa servo-piston` actuated in one direction by hydraulic pressure, `controlled by a `valve 4actuated by the governor, against oppositionby fa spring urging the piston in the opposite direction. The piston is connected with a cam which 4may cooperate with a manually positioned vcam follower whereby, under the Aconditions mentioned heretofore as example, the travel of the piston in either direction `may be ,limited ,or fthe piston may be forced to move by manual control.

The control of the demanding movement by the governor is substantially independent .of operation of the torque units because Change in blade angle does not have any appreoableef feet on the -ow rate or pressures at the governorcontrolled valve. Since the hydraulicrsystem directly controlled by the governor Jis separate from the hydraulic system of tbe-torque units which require relatively high `operations pressures and ows, the former system isnot required to operate at torque unit operating pressures and flows; but ,it can operate at pressures andflows which are considerably lower than torque unit operating pressures. Hence the `disturbing efiect of high ow forces and pressures upon the fgoverfllor controlled valve Ais minimized. i

A further object of the invention is to provide for featherne and unfeatherns- This is eocomplished by a system of control which provides :for selectively conditioning the distributor valve (through control by the governor or by manual kcontrol liro case the ,sovernorfailw for making the feathering or the unfeathering connections between the pressure line andthe torque umts. and for conditioning the accumulator control valve for dseharseof the accumulator in order to effect the selected feathering or unfeathering operation.

A further object is to provide a control system capable of operation either with or `.without the use of a propeller-pitch responsive governor'. ,l

Further objects ,and advantages of the present invention will be apparent from the Yfollowing description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings: i

Figs. l and 2 taken tog-ether AcO lli'ilitilte :a 1ongitudinal sectional view of a propeller hub and regulator assembly embodying the present yinvertton, Fie. .1 being a ,sectional View taken, in een i eral, on the line lm-l of Fig. `3. 1

3 is a seetional viso/,on `the line-fi-B .of

o o Fig. l. Fig. 3A shows a modiiication of Fig. 3.

Figs. 4, 5, 6, 7 and 7A are sectional views taken, respectively, on lines i-d, 5 5, @-5, 7-7 and 'lA- TA of Fig. 3,

Fig. 8 is a plan view of the regulatormounting Iplate without theinstruments shown in Fig. 3 mounted thereon.

Figs. 9, 10, 11 and 12 are sectional views, taken respectively, on the lines 9 9, M-itl, Ele-1l and |2|2 of Fig. 8.

Fig. 13 is a View of the governor shown in Fig. 3, said view being taken in the direction of the arrow i3 of Fig. 3.

Fig. 14 is a sectional view on the line ill-ifi of Fig. 15.

Fig. 15 is a sectional view on the line 15--15 of Fig. 13.

Fig. 15 is a sectional View on the line iti-i5 of Fig. 15.

VFig. 17 is a side view in the-direction oi.' the a arrow i of Fig. 13.

Fig. 18 is a sectional view oi a valve shown in Fig. 15, said view being twice the scale of Fig. 15.

Fig. 19 is a View, in the direction ci the arrow i9 of Fig. 17, of the governor valve body.

Fig. 20 is a sectional view on the line 2t-25 of Fig. 19.

Fig. 21 is a sectional view ci the diiferentiai mechanism 310 shown in Fig. 3, Fig. 21 being taken on the line 2 l-EI of Fig'. 22.

Fig. 22 is a sectional view on the line 22h-'22 Figs. 25 and 25A are modified forms of cam of Fig. 24.

Fig. 26 is a sectional viewv on the line 25-2i3 of Fig. 27 of the distributor valve |519.

Figs. 27 and 27A are sectional views taken, re-

spectively, on the lines 21-27 and 21A-21A of Fig. 26.

Fig. 28 is a sectional View on the line 25-20 of Fig. 29 of the accumulator control valve 129.

Fig. 29 is a view in the direction of the arrow 29 of Fig. 28.

Fig. 30 is a sectional View on the line 311-39 of Figs. 28 and 29.

Fig. 31 is a view similar to Fig. 3D showing certain parts in other positions.

Fig. 32 is a plan view, partly in section, of the flow control valve 2&9.

Fig. 33 is a View in the direction oi the arrow 33 of Fig. 32.

Fig. 34 is a View in the direction of the arrow 34 of Fig. 33.

' Fig. 35 is a View in the direction of the arrow '35 of Fig. 32.

Fig. 36 is a sectional view on line 3 5-35 of Fig. 32.

Fig. 37 is a sectional view on the line 31-37 of Fig. 33. y

Fig. 38 is a sectional View on the line 38-38 'of Fig. 32.

Fig. 39 is a sectional view on the line .1Q-59 Fig. 40 is an hydraulic circuit diagram.

Figs. 4l and 42 are charts illustrating certain functions of the system.

Referring to Fig. 1, 5S designates a tubular engine driven shaft having external splines 5| inating with internal splines provided by a propeller hub 52. Hub 52 is clamped between rings 53 and 54 of wedge-shaped cross section, ring 53 being by snap ring f der 59 which extends a substantial distance beyond the left end or" hub 52 and receives a cap 50 (Fig. 2) sealed by packing ring 11| and retained The central opening 53 in the cap G0 is closed by a plug 0d through which extends a valve 05 such as used in pneumatic tires. Through this check valve t5, gas is forced under pressure within the chamber between the cap 50 and a piston G5 sldable within the cylinder 59 and sealed by a packing ring Sl'. When the accumulator has been loaded with gas under pressure, the valve t5 is covered by a cap 90. The turning of the nut 55 is effected by turning the cylinder by means of a Spanner wrench having internal splines to fit the external splines 09 o1 the cylinder 5t. rhe cylinder 55 is locked in posi-s tion by a plate 'l5 having internal splines engaging splines 59 and having tangs 7| received by certain tending upwardly from the plate 90.

ones of a plurality of notches 72 in the end of a hub extension 52a. A snap ring l2 retains the plate 79. The groove 7d of cylinder 59 receives packing ring 'i5 which prevents the escaperof lubricant from chamber 75 between hub extension 52a and cylinder 59. Hub extension 52a is `secured to hub 52 by a clamping ring 80 through which screws di pass which are threaded into the hub 52.

Hub 52 provides tubular portions 02 each extending radially of the engine shaft axis and each receiving the root $33 of a propeller blade. Each root 83 is retained by a plurality of angularcontact bearings 611 located between a nut 85 threaded on the inner end of root 83 and a nut SS threaded into the tubular portion 82 and retained by a key 81 fitting into a notch 88, and being secured to ring 86 by a Screw 9. Ring 80 supports a seal ring 86a.

Each blade root 33 s connected by pins 9| with the ilange 92 of a cylinder 93 and with a plate 9G providing a bevel gear segment 05. Cylinder S3 and plate 94 are supported by ball bearing 95 which is supported by a pad or boss S1 of the hub 52 and which is retained by a plate 9S attached to pad 97 by a bolt 99 which threadedly engages the pad 97 and which has a tubular shank through which extends a tube |00 leading from a recess 97a to the space in the upper end of the cylinder 93 .between a cap |0| and a piston |02 Cap |01 is retained by a snap ring |03 and is sealed at |05. Piston |l2 is provided centrally with a tubular extension |05 surrounding the tube i and provides a packing gland |06 fitting around'the tube |05. Piston |02 isthreadedly connected with a sleeve |07 which is exteriorly helically splined at |00 to mate with interior helical splines H39 of cylinder 93. Sleeve |01 is interiorly helically splined at ||0 to mate with external helical splines of a sleeve ||2 ex- As piston |02 moves radially of the hub 52, it turns relative to sleeve I I2; and the cylinder 93 is caused to turn relative to piston sleeve |107 and to the stationary sleeve H2. In this way radial movements of the piston effect rotary movements of theblade roots, substantially as disclosed in Patent #2,307,101, Blanchard et al.

Thefbladefroots 83 are rotatively tied together by aemaster bevel gear supported vby a ball bearing |2| supported by' hub extension 52a. Gear |20 has a tubular hub |22 surrounding the accumulator cylinder 53 andl providing a gear |23 meshing with an idle gear |24 supported by a studV orV stub shaft |25 supported by hub extension 52a as shown in the lower left hand portion of Fig. l. Gear |24 meshes with a pinion |26 which drives a shaft |21 for a purpose to be described. Gears |24 and |26 are enclosed by a plate |28 to which is attached a cover |29 for the left end of shaft |21. Pinion |26- is'notdirectlyattached to the shaft |21 but has clutch-tooth engagement v'vith'a` disc |30 longitudinally spl'ined to shaft |21 Vand urged toward the pinion |26 by a spring |3| which isv retained a nut |32 'tl'ire'adedl on the shaft |21. The connection between pinion |26 and disc |30 being susceptible of'adjustment upon loosening of nut |32', the shaft |21 can be properly timed relative to the master gear |20. l

The regulator assembly isr designated in its entirety by numeral in Fig. li.` The instru.- ments of the regulator are enclosed within a housing provided by a plate |4| and a cover |42 f which are rotatable with the hub,V and by rings |43 and |44 which are non-rotatable. Ring |44 supports the inner race of a ball bearing |45, the outer race |46 of which is attached to cover |42.

A seal |41 is located between ring, |43 and cover |42.- A seal |48 is located between ring |44 and plate |4| and is supported by a ring |48d fixed to plate |4| and surrounding ring |44, for which ring |48a may provide a bearing. Assembly |40 retained on the hub 52 by a sleeve nut |49 threadedly engaging the hub at |49a and engaging plate |4|. A plate |56 is attached to ring |43 and retains a ring |5| having a handle |52 and providing an internal or ring gear |53 engageable with a plurality ci pinions |54 each connected with a shaft |55 having a screw |56 threaded into a ring |51, surrounding ring |44 and guided by studs |58 supported by ring |44 and providing locating doWels for ring |43. Ring |51 has an annular groove |59 for a purpose to be described. Screws |50a secure together' the rings |50, |43 and |44. RotationV of lever |52 and ring |51 effects axial movements of ring |51 which does not rotate with the propeller hub, because `ring |50 is provided with a'tang |60 engaging a notch |`6| 'in a plate |62 attached to the engine frame |63'.

The regulator assembly |40 rotates around the ring |51 and any manual control of instruments of the regulator must be effected throughconnections of the groove |59 of the ring |51. As shown in Fig. 3`, the regulator includes several pumps |65, |66, |61 and |68 Whose shafts are driven respectively by gears |65a, |66a, |6-1a and |68a, all meshing with a stationary gear |69 integral with or connected with the iiXed ring |44.

The inlets of these pumps are all connected with a Source of hydraulic liquid or oil contained in the reservoir provided by the plate |4| and cover |542, the rotating level of the liquid being such "that at leasty the inlets to the pump impeller 'wheels' (such as |6810) are submerged. Pump impeller Wheels for feeding oil to the pump inlets are necessary when the accumulator is supplied With 'oil from the reservoir of the unit |46; and thenlling of the accumulator with oil under pressure materially drops the rotating oil-level the reservoir. The reservoir is lled through holes |680 (Fighe).

an openingat the top nFig. 1 Which'Will-be closed Fig. 1 shovvslpump lialvvhich 'isfliiiel pumps'fl and |81. It is. connectedfby screws |6811` in the plate |4| said` screws being threaded into tapped Its. outlet is connectedz'with a hole |16 in a pad |1| which. isransfinsert inr the `casting ofr whichV plate |4| is: made.f Hole |10 leads to hole |12 in pad |'1|. Pressure oil `discharged by pump |558I flows. through passage |12, pipe |13 connected with al passage |14 in a pad |15 which receives a lter H16 (Fig. 6)` whose inlet is connected with passage |1-4andl` whose outleti's connected with passage |11 connected by `pipe |18 with passage |1f9of pad IBD/connected by a pipe |8'Ii with passage |82 of pad |183. Passage |82 leads to a lter |84 27a) located inthe recess |285. The outlet oi filter |84 is connected with passage |86 in `bloclt |81 of distributing valve |99 (Figsi 26 and 27'). -Block |811 supports a` valve cylinder |88 having an annular groove |89 connected with passage |861 and having ra dial passages |9`| connected with the space within the cylinder |88 and surrounding a valve stein |92 having lands |93 and |94 for controllingports |95 and |-9 6 respectively connected with grooves |91 and |98 respectively connected with passages |99 and 290 respectively which, as shown in Fig. 27,1are connected with the' interiors of filters 20| and 202 respectively located' in recesses 203 and 284 respectively and connected with passages 255 and 266 (Figi.- Sl) respectively connected with pipes 20M-201 and 208 respectively. Pipe 201 makes connections With branch passages 269 (Fig. 10) each leading to one side of the piston of a torque unit for decreasing pitch; and passage 268 is connected with branch passages 2|!) (Fig. 9i) each leading to the pitch increasing side of the piston of each torque unit. Fig. 1l shows hoW a connection between pipe 2&8 and one of the passages 2 I0 is made through an insert pad 201e. Valve stem |92 (Figs. 26 and 3) is urged toward a lever 211' by a spring 2 |5 contained within the stem |92 `and' conned by a plate 2id attached to the valve body |81. Stem |52 is moved down by a lever 2|1 pivote'd either at 2|8 or 2|8a (as shown in Fig. 26) by a screw 2|9`. Lever 2|1 is connected by a screw 222 with a link` 22| connected by a screw 222 with a lever 223 pivotally supported 'at 224 (Eig. 3) and actuated in a manner to be described later.

Pump |68 has a capacity sunicient for operation of the torque units at a moderate rate.. When extra fast operation ofthe torqueunits is required. the flow rate to the torque units is boostedV by the output of pumps |66 and |61, whose outlets are connected respectively with passages 223 and 221 of pads 228 and 229having passages 230 and 23| respectively connected by pipe 232. Passage 23| is connected by pipe 233 with passage 234 and hole 235 in pad 236 which has holes 231 and 238 connected by cross passage 239 and a pipe 2390, conncctedwith passage |12 of pad |15, The control of the flow of oil from the hole 235 to the passage 239 is obtainedby a now control valve unit 240 which will now be described with' reference to Figs.`32 through 39.

Flo'w control `valve unit The loW control unit 240 comprises a valve block 24| having a'pertured .lugs 242, 243'.. 244 adapted to be secured toplate |4| by screws 242a, 243a, 244e (Fig. 3), respectively, received by tapped holes 2421i, 243i), 244D, respectively; l(Eig. 8). Block 24| provides apass'age 245 aligned with :hole 238A connected with passage 239. Passage 245 leads to a valve Acy1nder2`46` whichreceives 7 a valve cylinder or guide 241 having packing grooves 248, 249 and 250 and having oil passage grooves 25| and '252 connected by radial port holes 25|a and 252a with the interior of the guide 241. The port holes 25m are controlled by a land 253 of a valve stem 25d attached to a head 255. Between the head 255 and the valve guide 241 there is located a control spring '256. Valve stem 254 is under control by centrifugal force acting in the direction of arrow 251 and by the spring 253 acting in the same direction. These forces are opposed by fluid pressure entering at 245 and acting upon the upper side of valve land 253. The stem 254 provides a flange or land 260 against which pressure fluid operates in the cylindrical space 25| below the land 26o. This space l23| receives oil pressure through a passage 282 opening into the bottom of the block 24| as shown in Fig. 34. Passage 232 is connected with passage 263 in pad 235 connected by passage 264 with in creased pitch passage 223. The pressure in cylinder 24S is effective upon an area whose diameter is the diameter of land 253. Any pressure in cylinder 26| is eective upon an area equal 1.*/4

times the squared diameter of land 235 less the squared diameter of rod 2% below land 255i.y

lTherefore when the increased pitch line 29S is carrying the pressure fiuid, there will be a tendency for stern 254 to move upwardly toward a position for blocking the ports 25m. Normally the valve blows off at various pressures increasing with increase oi resistance to blade angle change.

rlhe pressure fluid. released by blowoi discharged through holes 25H1, the groove 253i and thence through hole 235 (Fig. 32), passage $533, passage 261 to groove 283 in a valve guide 239 located in a bore 215. Groove 268 is connected by holes 21| with the bore 212 of valve guide 2M, said bore receiving a piston valve 213 attached to a stein 214 carrying a plate 215 against which a spring 218 acts to urge the stern 214 toward the right. Stem 214 has an annular flange 211 of greater area than the flange 213 where the stein 214 joins the piston valve 213. The bore 213 is connected by a passage 21.. with the cylinder 243 of the pressure control valve. When a certain minimum pressure obtains in the bore or cylinder` 21|?, the differential of the pressures acting on anges 211 and 213 will overcome the spring 213 whereupon the valve 213 will move left to uncover the ports 21| and pressure iluid will flow out the holes 289, the annular groove 28|, the bore 216 which, as shown in Fig. 39, is connected by passage 282 with a cavity 233' in a cover plate 283 and conms municating with the upper end of the cylinder 284 of the pump control valve thereby exerting pressure against land 286 provided by valve stem 285. Some of this pressure escapes through drain hole 288 (Figs. 32, 31 and 33). Land 236 is above drain hole 289 which, as shown in Figs. 37, 38 and 40, is connected with passage 23] connected with passage 235. Therefore, the pumps His and 61 connected with hole 235 (Fig. 8) will be connected with drain and they will not be operating under pressure. This condition exists when the torque units do not absorb the full capacity of the pump |83. When the torque units absorb the full capacity of pump |68, pressure in cylinder 246 drops and blow-off of the pressure oontrol valve ceases because valve land 253 will move up in Figs. 37 and Ll0 under the action of cenytrlfugal force exceeding the force of pressure upon land 253 to block port 25m. Blow-off pressure which had been in the cylinder 285, above land 286 leaks out through passage 285. Therefore,v under the action of centrifugal force exceeding pressure above valve 233, valve 235 'rises to block the drain 269 of pumps |35 and |61 and to connect ports and 29| (Fig. 38). Therefore, the output of pumps it and |61 flows past the check valve 292 into the valve-retaining recess 233 and through hole 231 and through passage 239, so that the combined output of pumps 15S, |61 and les is eective to operate the torque units at the desired rate. (Normally check valve 292 wouldl be held against its seat by the pressure from pump |8.)

When pressure fluid is flowing from the distributor valve E99 to the pitch increasing duct 2M (Fig. 8) pressure is applied through hole 262 to cylinder 23| (Fig. 37) thereby adding a force tending to move valve rod 23d upward.. This has the effect of limiting blow-oif pressure to a value only slightly greater than the requirements.

The cap 283 is sealed by ring 25% and secured by screws 233e. The valve 335 is retained by a plate Zell secured by screws 294e and having a notch 294D received by a groove 294e in the pressure control valve guide 231 thereby retaining the saine in position. v

Pump |35 is attached to plate Iil by screws lfib received by tapped holes vi650 (Fig. 3). Its gear Elite (Fig. 3) drives a shaft 5523 (Fig. 7) carrying a gear 52i meshing with a gear 522 carried by shaft 5213. Shaft 523 is journaled in bearings and 523 provided by plates i325 and'il respectively; and shaft 523 is journaled in bearings 528 and 53li provided by plates 525 and 521 respectively. A housing for gears 522 and 523 is provide-d by plates .325 and and an intermediate plate 2529, said plates being secured together by screws 53| threaded into a plate 55am. Gear Hia, which rotates clockwise in Fig. 3 against a shroud i553, picks up oil from the regulator housing (provided by plate and cover |42, Fig. l) and pushes it into a pocket 532 (Fig. 3) whence it iiows through passage 533 to the inlet of the gear housing. The gears 522 and 533 force the oil to the housing outlet 334 (Figs. 3 and 7A) which is connected with drain i535 through relief valve 535 and which is connected with hole 531 connected with passage in pad a and with pipe 296, passage in pad 238, pipe hole 299m in pad 291e. 'lhe construction of the pumps |53, |61 and i553 is similar to pump |65 except that they are each provided with an impeller wheel iitting a shroud (such as wheel |5310 and shroud |588) for effecting movement of oil into a pocket (like 532 of pump 5.35) from which oil flows to the pump inlet. The outlet (531, Fig. 1A) of pump itli is connected with a hole 295 in pad 2950i connected by pipe 293 connected with passage 231 in pad Zeil and connected by a pipe 299 with a hole 233s in a pad 261i). The pump relief valve 533 shown diagranimatioallyin Fig. fi() is built into the pump as shown in Fig. 7A..

The governor The governor 333, Figs. 3 and 13 to 2l), cornprises a valve body Sill providing a wing 32 having holes 3&3 and 334 and a wing 395 having a hole 335, Holes 352s and 303 receive screws 333m, 334e and 3Std which are received by tapped holes 33b, 324D and 3%?) in plate UH (Fig. S). A part of the valve body 33| is received byV a recess 3iia of the plate lili. Valve body Sill has a bore 35i? which receives a valve guide 3|! having annular grooves 3&2 and 3|3 connected respectively with the central bore Sid of the guide by ports SE2d and 3|3a. The ports 3|2a and 3|3a are controlled by the lands H25 and 3|3b respectively of a valve 3|5 which is urged upwardly 9 by.;oentrifugal `force as indicated by arrow 3|6 Valve .31.5, Fig. :18, is threadedly connected with a rod .3H provided With .a notch 3|8 in its upper end .to receive a cross pin 3|19 by `Which lthe valve 3| .5 can be locked in adjustment relative to the rod 311. Rod 3H proyides'a clevis 320 connected by `1oih..3.12| with .a lever 322 `urged downwardly `by a vspring .323 against a stop roller 3.24 or` against anadjustablenilcruin:roller.325. A .Screw .326 received by .the Wing ,33.2 passes through the outside branch 32'! of a Vil-shaped leaf spring member 33B. The other outside branch 3.2.3 is secured .by ascrew .33| tothe body 301. rIhe cehterportiop 3.29 ,i apertured to receive stud 332 .carried by lever 32.2 (Eig. le) `and which extends through a central .opening fthe spring retainer .33.3 .against which the spring .32.3 bears. The upper epd oi spring A,3.2.3 `bears .against the ila-nge ol .a sleeve 3.34 through which a screw 33e is threadede The sleeve 334 provides a notch .336 which receives a lug `337s of a plate 3.3.1 .attached by screws 338 to the body .395. .Plate .331.has `ariopehhe `33t` for receiving Screw .-33.5- .Sprroupding the open.- ine 339 the plateeil provides a serrated flange 340 receiving `similar serrations 34| .of the flange of the .screw 313.5.- ;The .adjustment of spring .323 is shade `by :applying ,a screw driver blade .to the upper .emi o f screw 335. Turning the screw causes it to `be cammeo downwardly by `the coaction of. the` serratiohs, :thereby permitting its rotation. Whilethe .screw 335 is being turned, theisleeye or :mit .334 is restrained fromrotation by y-irtueof its (engagement with the lus 3.3i@ .of the plate 3.3i.. Therefore `the put .334 .is caused to :moye axially .when the screw 33.5 is turned. Y

The screw .3.3.3.isretaiped `ih the desired position or :.adipstment by the serratiohs .330 and 3M 324 and 325 ageihstwhich the lever 322 bears.

Carriage 353 proyilesiagh apertured boss 352 (Fig.

16,) for receiying the shank 35,3 of a shoe 3554` which is yreceiyergsl by groove |519 `of ring |51 (Fig. 1.). `TP in 3325er supported by carriage 350 `piyotally Supports `roller axially .causes increment .of the .carriage 35D horizontally .as -yiewed in Fig. V15. Adjustmentof the roller 32,5 .horizontally .varies the 4-eiect of spring 3.23 in .opposing centrifugal force .acting upon the v a-lyelli. The carriage 353 `.provides a pin 333 passing' through ga roller 33'! :for engaging acam3f| (Fig. 2e) of a differential mechanism tobe described.

.Reierrihg to e, the `passa-ae :29e .is con nected with a `recess 353 which receives a lter 3,53 (Fig. 4), theioutlet 360 of rwfliicli is connected through .hole :33| (1F- tese and 20) andpassages 3.6.2 and zllwithkgroove.3| 3 (Fig. 15) of Valve guide .3|.|. .Groove 3M ifs connected with drain through passage 333. Plugs 3G2p.close theputer ende of -gthe .drill holes for the .phssage'liii and 35211,. the normal operating status of the governor 333. the Valve .3!.5 is so positioned as to partially close the drain ports 3I2a. When. the speed vis greater than. .that which would balance thceiect of eprice .32.3, yalye .31.5 moves up to decrease the .opening `.of the drain ports sito. When the speed is less :than Ithat which balances the effect of spring? the .Valye; 3 |15 moyessdown tc increase 4.the i.opening of :the l drain Perts .312m

Adjustment ofthe ring |51 r 1f! This produces .an .clrect prop `the eitierepiial mechanism which lwill :heyy Abe described.

Diferencial mechanism der ,311 containing a piston .3.148 having a .rod ..313

having Aits left :chil connected with a bracket .3.80

which provides .a cam 38| with which'roller3lil. oi the ecyerhor 3.00 .may cooperate. Bracket .38.9 i

has. a lue 3.8.2 which is notched io receive e roll 333 received by .asocket 3.84 .ih `body .31| .alle re* taipecl therein by pi-h 3.8.3 .A spring .38.6 .surf rounding the :rod .3.3.2 .presses against the .hotly .31| and a Washer .3.8.1 which .bears against the bracket lug ,3.3.2 to urge .the piston 3.7.8 :toward the left thereby :resisting fluid pressure which may prec it toward the right.

The Ypiston 3.1.8 has .a roll portion .38.9 `prpyiding a rack 3 30 which meshes with .a gear .33| connected with ring scar 39.2 loosely ioprpalerl or. shaft 39.3,. .Ring scar .392.mesh-cswithp1apet gears .394 .meshing with sun gear .3.35 hired 3.0 shaft .3.3.3. .e coupling .336 .connects shaft `3.3.3 with shaft -.L21 Fig...5 operated by the .master bevel scar lL23 (Fie. f1.) .and therefore rotating during .a change .ip blade .angle- -shaft .3.9.3 ...is rotatably `supper.ted .by .a .strap .39,1 attached by nuts 13.9.8 and screws .39.9 to .body .31| .ape .to plate 3l l which supports .a bearing bushing .4.0.1 for shaft 393.

The planet sears 3.9.4 .are Arotatable pppn Pins 4.9.2. the .left ends oi which .are supported by .a ring .4.0.3 carrying .a bearing bushing 404 supported by shaft 393- Thc .right end .portions of Vpins .4.0.2 are .supported by .a cam .plate 4.0.5 rotatably sopporto@ by the .bearing .bushing 40|.- Tne `outer peripheral surface of the plate .405 provides 1a carp 4.06 .havlhe its low dwell atc (Fig. 23.) and risiheto a .high dwellb through a .small angle.

Cam 406 engages a follower roller 4 0] on-lever 2.213 (llis- ..39 and .creed toward the .carri by the spring 2.1.5 which isfwithin .the valve .stem |92 o .the distributor valve .|90 (Fig. 26). As

will be explained later, the distributor .valve is under .lille control of .cam 4,0 6 which is under the control of .torque phits (acting through the master .bevel `gear 4I ZL'I and plain `.gea-r ||23 and shaft .1.2.1 and .shaft .3.9.3. son gear 395 and planet gears (3.3.4)l and under .control either by `the .cam 334 or by the servo-motor of the (differential, the Vpiston of which hasa .cohtrollihg-elect-on cam A03 through .the rack 3.90. the gear 139|. ring ecar.392 .and plahetgears .3.9.4.

Accumulator controlnalve is connected with hole 424 connected with hole 425 in body 42| connected with cylinder 425 closed by a cover 427 sealed at 428, Fig. 28. Cylinder 425 receives a spring 429 bearing against a lpiston 436 attached to a valve stem 43| and lhaving a frustro-conical valve portion 432 adapted to engage a similar formed seat 433 provided at the shoulder between the larger cylinder 426 and a smaller cylinder 434. Cylinder 434 cooperates with a piston provided by flanges 435 of valve stem 43| with packing 435 between the fianges. Cylinder 434 merges with an enlarged cylindrical portion 437 for receiving the head 436 of stem 43|', said head having a screw driver slot 436 for receiving a screw driver blade in order to hold the valve rod 43| stationary while turning the nut 435e screwed on the end 4345 of the rod in order to clamp the piston 455 against the flange 43m of the rod. The right end of the cylinder 437 is closed by a bracket 446 attached by screws 444 and providing a pivot at 442 for a lever 443 into which is threaded a screw 444 having a hex head or pad 445 and secured in the desired position of adjustment relative to the lever 443 by a selflocking nut 445. The pad 445 is adapted to engage a valve operating rod 447 slidable through a bushing 445 located in a recess 449 and sealed ,by rings 456 and 45|. A V-annular groove 452 of the bushing 448 is connected by passage 452a with cylinder 426, by passage 453 with cylinder 437 and by passages 454 with a bore 455 through which rod 447 extends, the left portion of the rod being less in diameter than the right portion so that a passage around the left portion and along bore 455 is provided, said passage being connected with passages 454 and being normally closed by a check valve 435 which is urged against its seat provided by the left end of bushing 448 by a spring 457 retained by a sleeve 458 screw threadedly engaging the bushing 448. Sleeve 45B is provided with a hole 458m. The sleeve 455 is located in a chamber 459 which is connected with cylinder 434 by passage 466 and which is connected with a passage 45! which is rconnected with hole 452 (Fig. 8) in insert pad |66 which is connected with passage 443 connected by pipe 464 with passage 465 connected by a longitudinally extending passage 456 (Figs. 12 and l) leading to the accumulator.

The accumulator is charged through the following circuit of the control valve unit 425: Hole 424 of insert pad |85 (Fig. 8), passage 425 of valve body 42|, passage 452a, passage 454, bore 455, out through check valve 455, sleeve 458, sleeve outlet 458e, hole 46|, hole 452, passage 463, pipe 464, passages 465 and 456. Back pressure from the accumulator prevents discharge through this passage by closing the check valve 456.

If, at the time the discharge of the accumulator is required for the purpose of completion of feathering when pump pressure falls, the check valve 456 is opened, then the accumulator can rst discharge back through passage 46|, opening 458e in sleeve 456, bore 455, passage 454, passage 453 to cylinder 437, thereby causing the piston land 435 and rod 43| to move left in order to disengage valve 432 from seat 433r and thereafter to cause piston 435 to move further to the left to partially uncover the hole 425, whereupon the accumulator may discharge directly through passage 46|, cylinder 459, passage 465, cylinder 434, cylinder 425,

hole 425, hole 424 of pad (Fig. 8,), and pipel itl leading to the distributor valve and thence to the torque units. When feathering is completed, the pressure differential on opposite sides of the piston 435 diminishes and permits the spring 429 to move the valve 432 against its seat 433 thereby preventing further discharge of the accumulator. For purposes of unfeathering, discharge of the accumulator can be effected by momentarily opening the check valve 455 by a movement of the rod 447.

The means for moving the rod 44E' left lto open the check valve 456 will now be described. This means is manually operated by movement of the grooved ring 57 into a feathering control position or into an unfeathering control position. For this purpose, the grooved ring |57 receives a shoe 475 having a shank 47| (Fig. 28) received by a bore in a tubular boss 472 and retained therein by pin 475. The boss 472 is integral with a carriage 474 which slides on rods 475 which are supported at their ends by a bracket 476 attached to the body 42| by screws 476. Carriage 474 has an arm 477 to which rivets 418 attach a block 479 which together with the arm 477' supports a pin 485 supporting a roller 48| engageable with a triangular cam 48?. having inclined faces 48211 and 452i). Cam 452 is integral with a plate 456 which is slidable horizontally as in Fig. 29 along a portion 484 of lever 443. Portion 454 has a slot 465 for receiving spacers 435 (Fig. 30) through which there extend the Shanks 457 of rivets having heads 458 slightly clearing the left face of the portion 484 as viewed in Fig. 30. rlhese rivets are secured as shown to the plate 485 by riveting over at 485. Therefore, it is' apparent that before any clockwise movement of the lever 445 can be eiected through motion of the carriage 474 in either direction (up or down in Fig. 30), the lost motion between the plate 433 and the lever part 484 must be taken up. The lost motion is such as will permit of conditioning the distributor valve to make the proper connections for feathering or unfeathering in advance of conditioning the accumulator control valve unit for discharge of the accumulator for feathering or unfeathering.

It is desirable to eiect movement of the carriage into the feathering control position in advance of the instant that feathering may be accelerated by ow from the accumulator. In order to make use of fluid energy stored in the accumulator, it is necessary not only to move the lever 445 left to open the valve 456, but also to hold the valve 455 open. This is necessary because, should the pump pressure be greater than the pressure available in the accumulator, the piston 430 will not move left sufficiently to uncover hole 425; and, therefore, sufficient time must elapse between time that the carriage 474 is moved to the feathering position and the time that piston 430 will have moved to uncover the hole 425 so that the system pressure will have dropped to a value less than the accumulator pressure as result of the blade angle becoming higher due to action of pump pressure, thereby reducing rotational speed. When pump pressure is down, the accumulator is ready to go into action because the valve 456 is already cocked. The valve unit 425 therefore provides a speed-responsive latch for holding the valve 456 in cocked position during the lapse of time referred to.

The speed-responsive latch is provided by thence'the valve |32 for applying fluid pressure to the torque unit C.

Overspeed error causes valve 315 to move up to increase the closing of port 3|2a. Pressure in cylinder 311 of differential 31d increases to overbalance spring 383 (equivalent of 326, Fig. 21) and piston 318 moves down to move rack 322 (equivalent of ring gear 392, Fig. 2l) down to rotate gear 3911 (equivalent of planet gears 33d, Fig. 22) counterclockwise while rack 335 (equivalent of gear 395, Fig. 22) remains stationary. Cam 425 (equivalent of cam i, Fig. 23) moves down to cause distributor valve |32 to move right to connect the lower end of torque unit cylinder CWith pressure thereby causing piston P to move up to increase the pitch of blades B, thereby increasing the torque required to rotate the propeller and reducing the engine speed. As piston Pmoves up, rack 395' moves up and causes up- Ward movement of cam 35 which allows spring 2|5 to move valve |92 toward equilibrium position.

Underspeed error causes governor valve 3|5 to move down to increase the opening of port EiZa, thereby reducing the pressure in cylinder 311 and permitting the spring 336 to move piston 318 up. This results in decrease of blade angle to permit increase of engine speed..

Under conditions of engine starting, roller 331 is so placed by lever 56|) as to be contacted by surface 38m of cam 38 There being practically no pressure above piston 318, upward movement of the piston 318 by spring 336 is limited by engagement of cam surface 38m with roller 351. rEhis limits the blade angle to a low positive value which requires the minimum torque absorption by the propeller in order to facilitate engine starting.

When engine starting is begun there is substantially no pressure of fluid from the pump |35 and in the channel 229 to the chamber 311, or it is so low that it has little or no opposing effect to the spring 38S for which reason the cam 33| is urged against the roller i51, but as soon as there is sufficient rotation of the propeller to create fluid pressure in the line 239 from the pump and the governor valve moves outward to restrict the port 3|2a the opposition to the spring 38e builds up and the cam 38| starts to move away from the roller 351 effecting a slight change in the blade adjustment through the racks, pinion and cam 423 with valve |32 for the engine idling conditions.

Under conditions of idling, after the engine becomes self-operative, the blade angle is limited by engagement of cam surface 35Std with roller 351 to the low positive value sunicient to maintain operation of the engine, but the angle may in fact be greater than the low positive value since the operationr of the governor 33t) will control sumciently to somewhat oppose the spring 38E, thereby spacing the cam 33| from the roller 351 and slightly shift the valve |82 through the action of the rack bars and pinion. Thus in both engine starting and engine idling the cam face 33m marks the low limit to which the blade angle may be set, and still provides for adjustment of blade angle to a satisfactory higher angle as the conditions may require and Within the provisions detailed by the curves of Fig. 42, later to be explained.

Control of governed speed is effected by movement of roller 325 left `of the position shown in Fig. 40 to reduce governed speed or to the right to increase governed speed. Position 325' of the roller 325 is the position for maximum speed of the engine as limited, for example, by an automatic fuel control FC. When thev roller 325 is at 325', roller 351 is at 351' in vertical alignment with the right end of cam surface 33| a. Further movement of roller 325 to the right of 325 such as at 351 for braking will not effect further increase of speed because the speed is limited by the automatic fuel governor. Therefore the governor spring 323 will move the valve 3|5 down further to open port slid, and the governor loses control because the pressure in cylinder 311 is not sufficient to balance the spring 386. Piston 318 then moves up until cam surface 38|b engages roller 351 at 351" thereby determining the blade angle according to the position of roller 351 to the right of position 351. Therefore, blade angle can be less, positively, than the value established by surface 32 ia and may extend into the negative pitch range according to the distance which roller 351 is moved right by lever 532. Therefore, a blade angle suitable for braking is obtained bw manual control.

During normal governed speed of the propeller pump |68 has a capacity sufficient for operation of the torque units C at a moderate rate, and the system has little need for supplement from the booster pumps |33 and |31. There may be conditions during governed speed, such as sudden and considerable speed change coincident with change in craft attitude, that may require a greater supply of pressure fluid for the torque units that can be promptly supplied by the pump |63. During feathering, unfeathering, and shift of blade pitch for braking, which is a negative pitch setting, and during reverse shift from braking back to positive pitch or governed speed operation, there is created such demands on the fluid pressure supply for the torque units that the pump |68 is sooner or later incapable of supplying enough pressure to complete promptly the functions called for. In any of those conditions resulting in inadequate supply of fluid pressure by the pump |68 to promptly actuate the torque units C there is a decided fall of pressure in the fluid pressure line 229 which is notJ only manifest in the distributor valve |99 but is also present in the flow control valve unit 215i). Pressure is low in the chamber 246 which permits centrifugal force and spring force to act upon valve stem 254 for closing port 25m, and pressure is also low in chamber 213 which reduces the differential on areas 211 and 213 so low as to be overcome by the force of spring 215 and permits the valve 213 to interrupt fluid flow through 21| to the chamber 284 of the pump control valve. Thus there is no drain back from the port 25m of the pressure control valve,

` and there is no iluid pressure in chamber 284 of the pump control -valve to oppose the outward movement of valve stem 285. Outward shifting of the stem 285 operates to connect ports 290 from the pumps and |61 with the port 22| which Yopens through the check valve 292 to the pressure source line 233. Thus, if there is any rotation of the propeller at the time that additional fluid pressure is called for it will be provided by the additional pumps as soon as the demand of additional pressure tends to reach the capacity of the pump |38. Coincidence of large fluid pressure demands and propellerrotation obtains during shift of blade pitch from positive range to negative for braking and reverse shift back to governed positive range, and generally during shift of blade pitch for feathering. During unfeathering shift at all times, and during feather- 191 suit the ,requirements for simple manual control of blade` angle `or for control by other means.

- it is to be understood that 4other formsmghtbe adopted, all `coming `Within the scope claims which follow; I y, Whatis claimed is as follows: i

1. In a system of controlfor anengine-propeller `power-plant having hydraulicallyoperated propeller-pitch `adjusting apparatus, alpressure system for `the apparatus `and a pressurepump driven by the plant, the combination comprising, a distributing valve inthe pressure system and connected with `the pump for controlling` pressure flow tothe apparatusVa differential mechanism disposedbetween the pressure system and the pitch adjusting apparatus for controlling the distributing valve andv having a first mechanism includinga rack bar actuable by the pressure system and movable in response to a demand for propeller pitch adjustment and a second mechanism including a rack bar movable in response to operation of said apparatus to eifectthe demanded propeller pitch adjustment andhaving an element actuatable by both rack barsfor controlling the distributing valve in response to the diiferential of the' movements of said mechanism, a speed responsive governor valve openwto the pressure system and operable upon thefirst said mechanism for controlling theidemanding movement of the differential mechanism :to effect a corrective propeller pitch adjustment when. there is a deviation from a selected governed speed, and manually operable means actuating thegovernorvalve for selecting the governed speedito be maintained. Y

`2. In a system of control for an `engine-propeller power-plant having hydraulically operated propeller-pitch adjusting apparatus, `a pressure systemforthe apparatus anda pressurepump driven bythe plant, the combination comprising.

a distributing valve in the pressure system and connected with thepump for controlling pressure iiow to the apparatus, a differentialv mechanism disposed between the 4pressure system, andthe pitch adjusting apparatus for ,controlling the dis-` trbuting valve and having a first mechanism including a rack bar actuatable by the pressure system and movable in `response to a demand for propeller pitch adjustment and a second mechanism including a rack barmovable in response to operation of said apparatus to effect the clemanded propeller pitch adjustment and having an element actuable by `both rack bars for con-` trolling the distributing valve in response to the differential of the movements of `said mechanisms, a speedV responsive governor-valve open to the pressure system and operable upon the first said vmechanism for controlling the demanding movement'of the differential mechanism to effect a corrective propeller pitch adjustment when there `is a deviation from a selected` governed speed, `manually operable means actuating the governor valve for selecting the governed speed to bemaintained, and means including a part of said yiirst mechanism operable under manual control `for, `conditioning rthe diiferentiahunder engine `starting and ;idling` conditions', Atoobtain a certain, propeller pitch adjustment suitableto facilitate the engine starting operation and to maintain operation of the engine duringidling when control by the governor is unsatisfactory.

3. In asystem of ,Y control for an engine-propeller power-plant having hydraulically operated propeller-pitch adjusting apparatua, alipressure system for the apparatus anda pressure pump driven by the plant, `the combination comprising. a vdistributing valve inthe pressure system and connectedI with the pump `for controlling. pressure `flow to the aparatus, adiiferential mechanism `disposed between the pressurewsystem and the pitch adjusting apparatusfor controlling the distributing valve andhaving a first mechanism including a rack bar. actuatable vby the pressure system and movable in `response to a demand for propellerpitch adjustment anda second-mechanismincluding a rackbar movable in response to operation of said `aparatus to effect the` demanded propellerpitch adjustment and having an element actuatable by both rack bars for controlling the distributing `valve in response to the differential .of the movements` of said mechanisms, a 'cam member, a` cam followermember engaging the'cam member,` one of said members being attached to a part of the first `mechanism of thedifferential, and means for effecting a movement of the other member toeifect a movement of `said second mechanism.

4. In a system of control for an engine-,pro-

peller power-plant having hydraulically operated i propeller-pitch adjusting apparatus, apressure system for the apparatus and a` pressurepump driven by the plant, the combination comprising,

a distributing valve in the pressure systemand connected with the pump for` controlling pressure ovv to the apparatus, a diiferentialmechanism disposed between the pressure system andthe pitch adjusting apparatus for controlling the distributing `valve and having a rstmechanism including a rack bar actuatable by the pressure system andmovable in response to a demand for propeller pitchadjustment and a second mechanism including a rack bar movable in response to operation of said apparatus ,to effect the demanded propeller. pitch` adjustment and having an element a-ctuatable by both rack bars for controlling thedistributing valve in response to the differential of the movements of saldi mechanisms, a servo-motor for actuating therst sure system and connected with the pump for controlling pressure flow to the apparatus, a differential mechanism disposed between the prssure system and the pitch `adjusting apparatus for controlling the distributing valve and having a'irst mechanism including a `rack baractuatable l by the pressure `system and movable in response to a demand for propeller pitch adjustment and a `second mechanism including a rack bar movable in response to operationof saidapparatus to effect the demanded blade propeller pitch adliustment and having an element actuatable by both rack bars for controlling the distributing valve in response to the differential of the movements of said mechanisms, a servo-motor op- Vderived;'atleast forl the beginning of the shift.

from the stored pressure in the accumulator 59. Under those conditions trip of the valve 456 releases the pressure of the accumulator which flows through the passage 453 to the chamber 431 to unbalance the valve 432 which then opens to apply the accumulator pressure through valves 452a and 425 to the pressure line 239 to the distributor valve and the torque unit C which shifts the blades sufficiently that windmilling will ensue if the air is moving relative thereto, such as the craft being in flight. If unfeathering is done While the craft is at rest on the ground with the engine not operating, then the unfeathering function must be accomplished wholly by the pressure available in the accumulator, but if the craft is in flight, the unfeathering proceeds by accumulator pressure until the windmilling of the propeller either starts the engine or drives the pumps fast enough to develop sufficient pressure in the pressure line 239 and consequently in the chamber 426 to excel the potential of the accumulator. At the instant of shifting the control 50D for unfeathering, the pressure in line 239 is low vand the unit 24|] effects connection of the pumps |63 and |61 with the pressure line 239 through the ports 295, 23| and check valve 292 for supplementing the pump |38,

and the unit 240 also closes the drain from the pressure control valve port 25 la so that the stored potential of the accumulator is not wasted. The shift to feathering, unfeathering, braking and return from braking to the governed range ofpitch is effected by manual actuation of the lever 556 of Fig 40 corresponding to manual movement of the lever |52 of Fig. l, and is capable. of superposition of the governor control at any time.

Manual control of low blade angle is desirable because it'isfdiilcult to control low blade angle by governor actionfsince the ratio of increment of change of torque absorption by the propeller to increment of blade angle change is too low for proper control by the governor. Since engine speed. is limited by somemeans such as an automatic` fuel control, it is possible manually to render the governor inoperative to effect blade angle control bydcausing its spring to overbalance centrifugal. forcef acting upon its valve and, concurrently, manually to effect blade angle control suitable for braking.

When. taXying on the ground is desired, rollers 325.l and 351 may be moved. to the right of positions 325' land 351 respectively. The governor loses control because spring, 32 3 overbalances centrifugal forcey oirvalve 3*!5 at engine taxying speed. Roller 3571 is engaged by cam surface 38|?)- according to the position of roller 351 to the right of 35.1'. By moving lever- 530', roller 351 and consequently cam 33| may be positioned for forward motion of the airplane or for reverse motion or for stopping.

When feathering is desired, lever 530 is moved counterclockwise tov feathering control position to condition the governor, by' extreme left movement of roller 325 to the left of the center line of. action. of spring 323, for feathering. Spring 323 will then assist centrifugal force to move valve 3|5 upto closeport 3120. thereby conditioning,y through the differential 310, the distributor |90 for feathering. If the hydraulic systemV of then governor should fail toA provide adequate pressure iny cylinder 311, spring 386 will urge `cam surface 33|c toward. roller 351. Therefore left movement of roller 351 into position corre'- sponding to the feathering position of roller 325, causes cam 38| to be moved down by the action of roller 351 on surface 38 lc so that the distributor 95 will be conditioned for featherlng. When the governor fails to effect feathering in Vre'- sponse to extreme counterclockwise movement of lever 50B, said movement of lever 50D effects through the coaction of roller 351 and cam surface 3S|c the control of the torque units for feathering.

Cam 38| in Fig. 25' adds to cam 38| the surface 38|d which may coact with the roller 351 so as to limit downward movement of piston 318 under governor action, thereby limiting the higher blade angles obtained to proper values in case of failure of the governor to function properly. For example, improper governor action might result from sticking of the valve 3|5 in a position causing too much increase of pres sure in cylinder 311.

Fig. 42 shows maximum and minimum blade angles corresponding to position of control ring |51 (Fig. l) which actuate's the carriages 350 and 414 which` are represented in Fig. 40' by the part 50|'. Line P-Q-R-S represents the low limit of blade angle as oont'rolled'manually, by the coaction of roller 351 with the cam surfaces 38|c, 38| a, 38H3. Line l=-'I*U-Vi represents the maximum values of blade angle as limited bythe coactionV of roller 351L with cam surface 38|d. Line W-X represents governor speed settings for lvarious positions of control ring |51. The blade anglev for various governor settings in the working range can lie between the maximum T-U determined by cam. surface 38|d and the minimum .Q1-R. determined by surface 38 la, said minimum being the minimum angle for which governing isv possible at ground level, and being a satisfactory angle for engine starting and for idling. For positions of Vcontrol ring |51 to the right of the maximum yspeed range, the blade angle'can be between the maximum values represented by U-, V and the minimum values repre sented by R-S which are the values which exist when braking or taxying. T-P represents the maximum angle when' going into featheri'ng by governor control and Q-P represents angle when going into feathering as resultY of manual control,

the' governor being non-operative to effect feathering.

In case of failure of the hydraulic system of the governor 303 or in case the governor fails to establish a pressure in the cylinder 311 of the differential' 310 sufficient to overcome the spring 385', direct manual control of blade angle isv still provided by moving lever |52 (Fig. l)- which is represented by lever 5110 (Fig. 40).

The system can be adapted for use without the propeller-speed responsive governor 300 and its hydraulic system if it is desired to control blade angle manually or by some automatic device external' to the system. In such case the piston 313 off the differential unit 310 would still serve as a spring abutment member' and the cylinder 311 as a guide for the rod 319 which the spring 386 wouldurge upwardly so that the caml on the upper end of rod 315 would engage the roller 351 which is supported for adjustment in a direction parallel to the propeller hub axis. For this purpose the governor body 30| might be retained to provide a support for the carriage 350 (Fig. 16) which carries the roller 351 and the shoe 354 for engaging thev control ring |51 (Fig. 3). The cam on the end of rod 319 would. be shaped to ama-,ese

erated by' fluid pressure: lor actuating the .first mechanism of `the differential in the direction` of propeller ,pitch adjustment increase, `an independent pressure system .for operating saidl servomotor and-.including a second pump driven. by the plant providing asource of fluid under pressure, a spring actuating theilrst mechanism, in the di.- rection of propeller pitch adjustment decrease,v

a, speed'responsive governor valve.Y open. tothe blade angle change apparatus, a `pressure system for the. apparatus. a pressure pump driven,

by the. plant, and a. distributing. valve in the` pressure system and connected with the pumpA for Vcontrolling pressure flow to the apparatus, a differential mechanism disposed `between the pressure system and the pitch adjusting apparatusv for. controlling the distributing valve and. having a first mechanism including ,a rack bar.

actuatable` by the pressure system and movable in responseto` a demand `for blade angle change and a second mechanism includingl a rack bar movable in respon-Seto operation of said apparatus toy effect the demanded bladeangle change and having an element autuatable by both rack bars tor controlling` the distributing valve in ren sponse to` thedifferential of the movements of 8;. In a hydraulically ycontrolled, constant.speedV propeller mechanismI having` pitch` shiftable blades,. the combination comprising, afspeed rez-- sponsiv. e. governor valve. fory sensing speed change and for applying a. corrective. unction to.` the` blades, means providing a relatively Alovv poten-1 tial pressure. source .connected with and! con- 4trolled `by said. governor valve,Y means` providing a iluidpressure responsive. differential mechanism `connected withv said pressure source and` governor valve forL introducingr the governor ap` plied corrective function to the blades.. a. blade` torque unit reversiblyy actuatable. for `'shifting the pitch, of the blades, a distributor valve actuated by the ydifferential mechanism for applying fluid pressure to the. torque: units, meansy providing'a.

` realtively hight Vpotential pressure source `con@ nected. to said distributor valve forapplication to. the said torque. units', and means including a.

; pari: of said differential mechanism fori actuating said distributor valve; for applying said highV `po` tential pressure to the torque unit when thefgov ernorzapplied. corrective function isxintroducedf by i said differential mechanism.

9.. a` hydraulically controlled constant speed= propeller mechanism having pitch.` shiitable blades',4 the, combination comprising,` a speed re sponsive'. governor valve. for sensing' speed changey and for applying a. corrective function toi the saidt mechanisms,. a servo-motor` operated by actuating the servo-motor, andmeans includingA a part of said first mechanism operableunder manual control for variably limiting pitch-conn trolling movement of said iirstfnlechanism.

7i A system of controlfor an. engine-propeller power-pla`nt comprising, hydraulically operated 'f blade angle change' adjusting apparatus, 1 a pres-3` sure systemA for the apparatus, a pressure pump driven by ,thei plant, and a distributing val-ve in the pressure system and connected-with the pump for controlling pressure flow to theapparati-15 diferential mechanism disposed" between the pressure; system andA the pitch. adjustingapi para-tus. tor controlli-ngthe. distributingvalve and.

havingl a first mechanism including a 4raclr bar actuatablez by the pressure system. andf movable in, response to` a demand for1 blade angle change and a second mechanism including arack bar movable, in response to operation of. said apparatus to effect the demanded bladey angle change and having an element. actuatable by both rack.

bars for controlling the distributing.` valve in rea spense to the` differential of the movements oilv said mechanisms, a speed responsive. governor valve open to the pressure system and" operable upon the first said mechanism 'for controlling the rstmechanismof the differential, means for ad-` justing the governor to maintain variousspcedsy means for'variably limiting the pitch-controlling movementsof said mechanism, and a device for concurrently operating both said'means.

blades, manually operated means for selecting the speed level atwhich the` governor valve is `to sense and. correct, means. providing a differential mechanism having av first part operable by said manual means andi responsive to the corrective functions of said governor valve and havinga second'. part: r'esponsiveto'y shift: of said blades,` alfiuid pressure servo responding tosaidgovernor for actuating: the said' first part, a` fluid pressure source connected to said governor valve andtor the servo-Ir-Iotor` oi said: first, part of .the difieren tial. mechanism, a blade torque unitreversibly actuatable for shiftingthe pitch of the. blades', a distributor valve actuated by the differential mechanism for applying fluid `pressure tol the. torque. units,A means providing a relatively high potential pressure source connected to said dis-l tributor valve, and means including a partfmov-l ableby either partof saidl differential n'iec'lian-ism4 for actuating said distributor valve for applying' said high potential. pressure to the torque lectively conditions` the. propeller mechanismifor additional; functions. as, feathering, unfeathering.`

negative, pito-b.-

restoration to positivepitc-h, and means including a lvariable. cam actuator and `the. `moving elementrof the fluid pressure.

y whenthepropelleris rotating at speeds.notssatl` servo interposed between said; manually operated meansV and. saldi differential mechanism. whereby`=` manualv control of the torque units is superim.I posedon the governor applied corrective function isfactorily controlledbysaid governor; f., A

1-1. in a hydraulically controlled constan-tspeed' propeller mechanism havingpitch. shiitableblades,A the combination. comprisingy a, .blade torque unit for-changing .the blade pitch, a dis-- y tributor valve for applying fluid pressure tothe torque unit, means` providing a fluidlpressure source` communicating with the distributor valve* and, including a plurality of substantially comfor connecting and disconnecting the delivery of certain 'of said pumps to the fluid pressure source asdemands of fluid potential by said distributor valve 'are varied, a pressure storage means, and a control valve connecting the pressure storage means with the fluid pressure source, speed sensitive means for actuating said distributor valve including a governor valve responding to propellerrotation', e, differential mechanism and aseparate source of fluid pressure for said governor valveysaid differential mechanism including `a first part responsive to control by said governor valve, a second part responsive to pitch shifting movement of said blade and a third partiinterconnecting said rst and second parts for actuating :said distributor valve, manually controlled means for selecting the speed level at which the governor valve will control and for effecting control of said pressure storage control means, and means including a part of said differential mechanism cooperating with the manually controlled means for eecting actuation of said distributor valve for speeds outside of the range of governed speeds for said governor valve, whereby when said pressure storage means control valve is opened to apply the stored pressure to the fluid pressure source for the distributor valve, said differential mechanism will be actuated for control ofthe distributor valve irrespective of the inability of the governor valve to effect its control.

12. The combination set forth in claim ll, wherein speed responsive latch means operatively connected with and actuated by movement of the manually controlled means outside of the range of governed speeds operates to maintain the control valve-for the pressure storage means open to the pressure source upon predetermined actuation of the manual means until the pressure source falls in potential to a point below the potential of the stored pressure potential.

,'13.,1n a hydraulically controlled constant speed propeller mechanism having pitch shiftable blades,v the combination comprising, a speed responsivegovernor valve for sensing speed change and for applying a corrective function to .the blades, means providing a relatively low potential pressure source for said governor valve, manually operated means actuating the governor valve for selecting the speed level at which said governor valve will sense a speed change and apply a corrective function, and for selecting extremes of bladel shift at either end of the governed speed range, means providing a differential mechanism having a first part cooperable with said manually=control1ed means and under theinfluence of the corrective function of said governor'valve', and having a second part responsive to blade shifting movement, fluid pressure means for shifting the blades including a distributor valve under the control of the dierential mechanism anda separate fluid pressure system connected with said distributor valve, means for varying the supply of fluid in said latter system as the needs of the pressure application by said distributor valve are demanded including a principal .pump supplying pressure during normal speed governing operation, and additional pumps with a oW control valve responsive to low pressure potential in said system for adding te the system the delivery of the additional pumps, whereby selection by the manual control means of extremes of blade shift may be manually controlled should the governor valve fail to adequately control.

14.In a system of control for an engine-propeller power-plant having hydraulically operated propeller-pitch adjusting apparatus, a pressure system for the apparatus and a pressure pump driven by the plant, the combination comprising, a distributing valve in the pressure system and connectedwith the pump for controlling pressure flow to the apparatus, a differential mechanism disposed between the pressure'system and the pitch adjusting apparatus for controlling the distributing valve and having a first mechanism including a rack bar actuatable by the pressure system and movable in response to a demand for propeller pitch'adjustment and a second mechanism including a rack bar movable in response to operation of said apparatus to effect the demanded propeller pitch adjustment and having an element actuatable by both rack bars for controlling the distributing valve in response to the 'differential of the movements of said mechanisms, a speed responsive governor valve open to the pressure system and operable upon the first said mechanism for controlling the `demanding movement of the differential mechanism lto effect a corrective propeller pitch adjustment when there is a deviation from a selectedgoverned speed, manually operable means actuating the governor valve for selecting the governed sped to be maintained, and means under manual control for conditioning the differential to obtain the feathering propeller pitch adjustmentunder conditions Where the governor fails to effect feathering although manually conditioned to do so, said last recited means including said rackA bar of said first mechanism, a cam member operatively connected to the said rack bar and a cam follower engaging said member.

15. vIn a system of control for an engine-propellerpower-plant having hydraulically operated propeller-pitch adjusting apparatus, a pressure system for the apparatus and a pressure pump driven by the plant, the combination comprising, a distributing'valvev in the pressure system and connected .with the pump for controlling pressure flow tothe apparatus, a differential mechanism disposed between the pressure system and the pitch adjusting apparatus for controlling the distributing valve and'having a first mechanism including a rack bar actuatable by the pressure system and movable in response to a demand for propeller pitch adjustment and a second mechanism including a rack bar movable in response to operation of said apparatus to effect the demanded propeller pitch adjustment and having w an element `actuatable by both rack bars for controlling the distributing valve in response to the differential of the movements of said mechanismaa speed responsive governor valve open to the pressure system and operable upon the first said mechanism for controlling the demanding movement of the differential mechanism to effect a corrective propeller pitch adjustment when there is a deviation from a selected governed speed, manuallyoperable means actuating the governor valve for selecting the governed speed to be maintained, and means under manual control for conditioning the differential to connek the propeller pitch adjustment to a certain range of -high limits under condition'swhere the governor fails to vmaintain .the propeller pitch adjustment Within said high range, said last recited means including said rack bar of said first mechanism, a member operatively connected to the said rack bar and having a plurality of definitive 

